EDGE Math 8

Postulate 7. Segment Addition Postulate

If points A, B, and C are collinear and point B lies between points A and C, then

A B + B C = A C .

Refer to the following figure:

Since $A B = 6$ and $B C = 8,$ then using the Segment Addition Postulate,

A C = A B + B C = 6 + 8 = 14.

In this case, point B lies between points A and C.

Definition

Point B lies between points A and C if and only if A, B, and C are distinct points on the same line and

A B + B C = A C .

Study how the definition of the term "between" is used in the next example.